Vasa praevia occurs when the fetal vessels run through the free placental membranes. Unprotected by placental tissue or Wharton’s jelly of the umbilical cord, a vasa praevia is likely to rupture in active labour, or when amniotomy is performed to induce or augment labour, in particular when located near or over the cervix, under the fetal presenting part. Vasa praevia is classified as type I when the vessel is connected to a velamentous umbilical cord, and type II when it connects the placenta with a succenturiate or accessory lobe.
Vasa praevia may be diagnosed during early labour by vaginal examination, detecting the pulsating fetal vessels inside the internal os, or by the presence of dark-red vaginal bleeding and acute fetal compromise after spontaneous or artificial rupture of the placental membranes. The fetal mortality rate in this situation is at least 60% despite urgent caesarean delivery. However, improved survival rates of over 95% have been reported where the diagnosis has been made antenatally by ultrasound followed by planned caesarean section.
Vasa praevia is uncommon in the general population with a prevalence ranging between 1 in 1200 and 1 in 5000 pregnancies, although the condition may have been under-reported.
The purpose of this guideline is to describe the diagnostic modalities and review the evidence-based approach to the clinical management of pregnancies complicated by vasa praevia.
Declaration of interests
Professor ERM Jauniaux FRCOG, London
Professor in Obstetrics and Fetal Medicine, Professor Jauniaux is a departmental Graduate Tutor (taught) at the EGA Institute for Women's Health, Faculty of Population Health Sciences, University College London. Professor Jauniaux is the co-founder and trustee of Medical aid films [MAF] a UK-registered charity [no 1121578] which provides multi-media programs for medical education and training in developing countries (www.medicalaidfilms.org). In addition, Professor Jauniaux is the co-founder of Sonic Womb, a research collaboration with UCL which aims to understand and recreate the sound in utero in order to improve neonatal incubators for premature babies.
Professor Z Alfirevic FRCOG, Liverpool
Mr AG Bhide FRCOG, London
Professor GJ Burton, University of Cambridge, UK
Professor SL Collins MRCOG, Oxford, UK
Professor Collins is the Vice Chairman of the International Society for Abnormally Invasive Placenta.
Professor R Silver, University of Utah, Salt Lake City, Utah, USA